Should astigmatism be corrected or not?

Why is it easy to fatigue if there is astigmatism but it is not corrected?

After correcting myopia with refractive error, a parallel light lens (concave lens) moves the focus that falls in front of the retina back to the retina to obtain a clear image. However, when viewed closer, the divergent light enters the fundus, and the first focus that comes closer is formed behind the retina, resulting in a blurred image. It then stimulates the lens to bulge and pulls the focus back to the retina. This is the mechanism of close-up, and the process of focusing is called regulation.

In the case of far-field refractive correction, the human eye needs to exert a 3D adjustment force to see a 33mm object clearly. If 100 degree myopia is not corrected, then only 2D adjustment force is required, but the amount of adjustment set will also be reduced. Different people have different AC/A, and the amount of adjustment set used will also be different, resulting in more varying degrees of relative exotropism of the eyes.

Assuming a person has simple astigmatism of -1.00 * 180, there is no refractive power in the 180 axis direction (horizontal direction), while the maximum refractive power in the 90 axis direction (vertical direction) is -1.00D. So when looking up, especially when looking at characters that are different horizontally and vertically, it's completely different. The vertical direction of this astigmatism requires less adjustment, while the horizontal direction requires more adjustment, resulting in a disorderly amount of adjustment, making it particularly prone to visual fatigue. Looking far does not require adjustment, so the symptoms of looking far are not obvious, only there are ghosting when looking at things.

When the astigmatism axis is at 180+-30, most people are more adaptable, followed by 90+-30. Look at things without deformation. However, a considerable number of people experience a sense of "spatial misalignment" when their axis is around 45/135 with oblique astigmatism, causing deformation when looking at things. The sum of the axial positions of both eyes is about 180, which is still acceptable. Not about 180 is the most difficult to adapt to.

The handling methods include:

1) It is possible to reduce the degree of astigmatism appropriately to alleviate symptoms, and generally, the degree of astigmatism correction should not exceed 75 degrees without significant sensation. It is not a problem to apply astigmatism above 200 degrees to 75% of the degree.

2) Off axis processing, the actual axis position is close to 180 or 90, generally not exceeding 10 axis positions. If one eye deviation can solve the problem, then there should be no deviation between two eyes.